Univ. Prof. Dr. Ing.

Bergs, Thomas

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  • Publication
    Fertigung für eine Kreislaufwirtschaft
    ( 2023-05-05)
    Bergs, Thomas
    ;
    Brimmers, Jens
    Die nachhaltige Nutzung der Ressourcen der Erde bildet das wesentliche Ziel unserer Gesellschaft. Für die Industrie und insbesondere produzierende Unternehmen ergeben sich dadurch völlig neue Herausforderungen in der Gestaltung ressourcenschonender Wertschöpfungsketten im Sinne der Kreislaufwirtschaft sowie der schnellen Realisierung nachhaltiger Produkte. Die erfolgreiche Implementierung der Kreislaufwirtschaft in produzierenden Unternehmen bedarf dabei verschiedener Ansätze - die Betrachtung der Umweltwirkung des Fertigungsprozesses, die Optimierung der fertigungsbedingten Produkteigenschaften, die Analyse der Korrelation zwischen Produktion und Nutzung sowie die Erarbeitung neuer Geschäftsmodelle zur Werterhaltung bzw. -steigerung. Der digitale Zwilling stellt hierfür das notwendige Werkzeug bzw. die Befähigung für eine erfolgreiche Umsetzung dieser Ansätze dar. Gleichzeitig ist der digitale Zwilling auch der wesentliche Befähiger für die schnelle Entwicklung von Fertigungsprozessen für die Bereitstellung nachhaltiger Produkte. Für diese beiden Ansätze werden in dem vorliegenden Beitrag verschiedene Beispiele vorgestellt, anhand derer die Möglichkeiten und Perspektiven einer nachhaltigen Produktion aufgezeigt werden. Ferner lassen sich aus den Beispielen Handlungsempfehlungen für die Umsetzung einer Kreislaufwirtschaft für produzierende Unternehmen ableiten.
  • Publication
    Manufacturing for a Circular Economy
    ( 2023-05-05)
    Bergs, Thomas
    ;
    Brimmers, Jens
    The sustainable use of the earth's resources forms the essential goal of our society. For industry, and in particular for manufacturing companies, this poses completely new challenges in the design of resource-conserving value chains in the sense of the circular economy and the rapid realization of sustainable products. The successful implementation of the circular economy in manufacturing companies requires different approaches - the consideration of the environmental impact of the manufacturing process, the optimization of the manufacturing-related product properties, the analysis of the correlation between production and use as well as the development of new business models to maintain or increase value. For this purpose, the digital twin represents the necessary tool or the enablement for a successful implementation of these approaches. At the same time, the digital twin is also the essential enabler for the rapid development of manufacturing processes for the provision of sustainable products. For both of these approaches, this paper presents various examples that are used to demonstrate the possibilities and perspectives of sustainable manufacturing. Furthermore, recommendations for action for the implementation of a circular economy for manufacturing companies can be derived from the examples.
  • Publication
    Influence of heat treatment and densification on the load capacity of sintered gears
    ( 2023)
    Scholzen, Philipp
    ;
    Rajaei, Ali
    ;
    Brimmers, Jens
    ;
    Hallstedt, Bengt
    ;
    Bergs, Thomas
    ;
    Broeckmann, Christoph
    The powder metallurgical manufacturing of gears offers a promising opportunity in terms of reducing the noise emission and increasing the power density. Sintered gears weigh less than conventional gears and potentially have a better noise-vibration-harshness behaviour, due to the remaining porosity. However, the potential of sintered gears for highly loaded applications is not fully utilised yet. Six variants of surface densified and case-hardened sintered gears from Astaloy Mo85 are tested to analyse the impact of the densification and case hardening depths on both the tooth root and flank load bearing capacities. Experimental investigations including metallography and computer tomography are carried out to characterise the microstructure. Furthermore, a simulation model is developed to quantitatively describe the residual stress and hardness profiles after the heat treatment. The load bearing capacity was improved by increasing the densification and case hardening depths, where the effect of the case hardening was identified to be predominant.
  • Publication
    Model for tool wear prediction in face hobbing plunging of bevel gears
    ( 2023)
    Kamratowski, M.
    ;
    Alexopoulos, Charalampos
    ;
    Brimmers, Jens
    ;
    Bergs, Thomas
    This paper deals with tool wear investigations for face hobbing plunging of bevel gears. Initially, the influence of process parameters and tool geometry on tool wear is analyzed both in cutting trials and with the help of the manufacturing simulation BEVELCUT. Subsequently, a tool wear model is presented. Input parameters into the model are tool and workpiece data as well as process parameters and chip characteristics. Through the manufacturing simulation BevelCut, which is based on a planar penetration algorithm, chip characteristics such as the maximum chip thickness hcu,max are calculated resolved in time and location along the blade's cutting edge. Combined with the local cutting speed, the chip characteristics are used to determine the thrust force, which is required to calculate the elastic workpiece deformation. The model coefficients are calibrated by multi-variable regression analysis using the results of the cutting trials and simulation results. The quality of the regression is determined with the help of equivalence tests. For verification, the process parameters and tool geometry are varied in series production and the tool wear is assessed. Finally, the modeled tool wear is compared to the measured tool wear.
  • Publication
    Investigation of the influence of asymmetrical profiles on the wear behavior in gear hobbing
    ( 2023)
    Janssen, C.
    ;
    Brimmers, Jens
    ;
    Bergs, Thomas
    Asymmetrical gears have advantages in applications with a preferred load direction, such as automotive transmissions or wind turbines. The operational behavior of gears with asymmetrical profiles has already been thoroughly investigated. However, there are very few studies on the manufacturability of gears with asymmetric profiles regarding the possible interactions between pressure angle composition, tool and process design. In this report, the influence of asymmetrical profiles on the wear behavior of hobs is analyzed for the first time. For this purpose, eight different tool variants have been defined for an investigation on tool wear behavior based upon fly-cutting trials. These variants consist of two symmetric and four asymmetric variants. In addition, two asymmetric variants with additional protuberance have been defined. Tool performance decreased within the fly-cutting trials with a low pressure angle on the leading flank and also in the presence of a protuberance. As the pressure angle increases on the leading flank, an increase on the tool life was observed.
  • Publication
    Experimental analysis on the influence of the tool micro geometry on the wear behavior in gear hobbing
    ( 2023)
    Kühn, Felix
    ;
    Hendricks, Steffen
    ;
    Troß, Nico
    ;
    Brimmers, Jens
    ;
    Bergs, Thomas
    Gear hobbing is a well-established manufacturing process for cylindrical spur gears. The cutting edge of a hobbing tool is, among others, characterized by the cutting edge radius and the form-factor K. The magnitude of these parameters is ideally chosen based on the machining conditions given by the workpiece and cutting material and the cutting parameters as well as the gear and tool geometry. However, the influence of the cutting edge geometry on tool life and wear behavior is hardly known, which complicates an optimized tool design. Furthermore, the preparation process regarding the coating thickness distribution on the wear behavior is equally relevant. Therefore, the objective was to identify the influence of the cutting edge radius, the form-factor K, and the preparation process on the wear behavior of gear hobbing tools made of powder metallurgical high-speed steel (PM-HSS). Fly-cutting trials were performed as an analogy process for gear hobbing in order to study the wear behavior and identify the respective tool lives. The trials indicated that the form-factor K influences the wear behavior, while a variation of the cutting edge radius did not have a significant effect. A homogenous coating thickness could extend the tool life significantly.
  • Publication
    Potential and challenges of tool condition monitoring in gear hobbing
    ( 2022)
    Hendricks, Steffen
    ;
    Troß, Nico
    ;
    Brimmers, Jens
    ;
    Bergs, Thomas
    Due to its high productivity, gear hobbing is one of the most frequently used manufacturing processes for the soft machining of cylindrical gears. One of the main objectives of an optimized manufacturing process is to maintain the required component quality while minimizing manufacturing costs. In both cases, knowledge of the tool wear is of great importance. Tool Condition Monitoring (TCM) provides a methodical approach to tracking tool wear during the process. In this report, various sensors are investigated with regard to their potential for TCM. Fly-cutting and hobbing experiments were conducted for this purpose. The signal data recorded during the tests were processed using high-pass filters, Hilbert transforms and Fast Fourier Transforms (FFT) in the time and frequency domain and evaluated according to various parameters. Based on the results, statements were made about the relationships between signal data and process conditions. For a precise evaluation of the tool condition, the combination of several sensors is necessary. In particular, the tool-side-mounted acoustic emission and acceleration sensors in combination with the power sensor and the airborne sound sensor showed increased amplitude values with increased wear. For the acceleration signals it could be shown that higher orders reacted more sensitively to increased tool wear. For the workpiece-side-mounted sensors, no meaningful results could be obtained due to the large distance to the cutting zone.
  • Publication
    Approach for multiscale modeling the thermomechanical tool load in gear hobbing
    ( 2022)
    Troß, Nico
    ;
    Brimmers, Jens
    ;
    Bergs, Thomas
    In this report, an approach is presented how a geometric penetration calculation can be combined with FE simulations to a multiscale model, which allows an efficient determination of the thermomechanical load in gear hobbing. FE simulations of the linear-orthogonal cut are used to derive approximate equations for calculating the cutting force and the rake face temperature. The hobbing process is then simulated with a geometric penetration calculation and uncut chip geometries are determined for each generating position. The uncut chip geometries serve as input variables for the derived equations, which are solved at each point of the cutting edge for each generating position. The cutting force is scaled according to the established procedure of discrete addition of the forces along the cutting edge over all individual cross-section elements. For the calculation of the temperature, an approach is presented how to consider a variable chip thickness profile. Based on this, the temperature distribution on the rake face is calculated. The model is verified on the one hand by cutting force measurements in machining trials and on the other hand by an FE simulation of a full engagement of a hob tooth.
  • Publication
    Consideration of micro-interaction in the modeling of generating gear grinding processes
    ( 2022)
    Oliveira Teixeira, Patricia de
    ;
    Brimmers, Jens
    ;
    Bergs, Thomas
    In grinding, the interaction between workpiece material and abrasive tool rotating at high speed generates high thermo-mechanical loads in the contact zone. If these loads reach critically high values, workpiece material properties deteriorate. To prevent the material deterioration, several models for thermomechanical analysis of grinding processes have been developed. In the most recent of these models, the thermo-mechanical energy is modelled considering the kinematic contact between the grains from the grinding wheel, the gear material and the chip. The consideration of the kinematic contact has the advantage of enabling the use of thermo-mechanical models on different dressing and grinding parameters without the need of extensive experimental investigations. In order to use these modern thermo-mechanical energy models, a penetration calculation model considering the tool topography, based on the grinding parameters and kinematics of the process is required. Such a kinematic topography analysis specifically for the process of generating gear grinding was not developed so far. This work presents a method for the integration of tool topography in an already existing geometric penetration calculation model for the simulation of generating gear grinding process. The method will allow the analysis of micro-interaction characteristics in the contact zone for the process of generating gear grinding.
  • Publication
    Evaluation of the influence of different milling parameters and tool wear on the rim zone of a 5-axis milled large gear
    ( 2022)
    Zachert, Christoph
    ;
    Greschert, René
    ;
    Schraknepper, Daniel
    ;
    Brimmers, Jens
    ;
    Bergs, Thomas
    Machining of gears by 5-axis milling allows additional degrees of freedom in gear design compared to conventional hobbing processes. Changes in the machining technology influence the surface integrity and, thus, the service life of the machined gears. For this reason, different machining parameters were investigated regarding their effects on the surface layer and subsequently on service life. In this paper, the residual stresses and microstructures of a large gear manufactured by 5-axis milling and the service life of test gears are analyzed. With the results from this paper, the surface integrity and service life can be predicted depending on the machining parameters.